Alt+Shift+ not work for me
Assuming it is not an issue with your keyboards shift key or an external program interfering with its function. (Network Mouse Applications usually interfere)

Goto User Preferences -> Input -> 3D View -> 3D View (Global) -> Activate Select Look for the Shift+Alt+Select Mouse Entry. It should have Toggle Selection and Enumerate checked. If it does not exist you have to create it or reset your whole keybindings.